Wood Wool Panel Edge Profiles Explained: B0, B5, B11, A24, E24 and C

2. august 2026

Thickness and fibre width get all the attention when a wood wool ceiling is specified. The edge profile gets almost none, and it is the choice that most visibly decides what the finished surface looks like. Two ceilings using identical 25 mm panels can read as one continuous textured plane or as a regular grid of separate tiles, purely because of how the panel edges were cut. Here is what each profile does and when to use it.

Why the edge matters more than it sounds

A wood wool panel is a cut slab of mineralised fibre. Leave the edge square and butt two panels together and you get a visible line where the fibre ends meet. Chamfer the edge and that line becomes a deliberate shadow groove. Rebate the edge and the panel can sit into a suspension grid with the frame hidden or exposed. The panel performs acoustically much the same either way. What changes is the read of the surface, the tolerance you have on site, and whether you can lift a panel out later to reach a service above.

Sonablock is supplied in seven profiles: B0, B5, B11, A24, E24, E24/90 and C. They fall into three families.

Family one: square and chamfered, for direct fixing

These are for screwing straight to battens or a timber grid, with no suspension system.

B0, square edge. The panel is cut clean at ninety degrees. Butt-jointed, it gives the closest thing to a continuous monolithic surface. This is the profile to choose when you want the ceiling to read as one texture and not as tiles. The trade-off is that it is the least forgiving: any deviation in the batten line shows up as an uneven joint, because there is no shadow to hide it in.
B5, small chamfer. A modest bevel on the visible edge. Butt two together and you get a fine V groove. This is the pragmatic default for most projects. It keeps the surface calm while giving the installer a few millimetres of forgiveness, because a slightly imperfect joint disappears into the groove rather than announcing itself.
B11, larger chamfer. A deeper bevel producing a pronounced shadow line. Here the grid is part of the design rather than something to hide. It suits large ceilings where an expressed module gives scale, and it is the most tolerant of the three on an imperfect substrate.

The rule of thumb: the bigger the chamfer, the more the joint pattern becomes a design feature and the less precise the carpentry has to be. On a renovation where the existing structure is not flat, B11 will save arguments.

Family two: rebated, for suspension grids

These are cut to sit in a T-grid ceiling system, the kind used across offices and public buildings where access above the ceiling matters.

A24. Rebated so the panel drops into a 24 mm exposed T-grid and sits with the grid flange visible. This is the conventional demountable ceiling look, and its advantage is entirely practical: any panel lifts out in seconds for access to cabling, ductwork or a valve.
E24. Rebated to conceal the 24 mm grid, so the panels sit proud and the frame disappears from view. You keep demountability but lose the visible metal line. This is the profile for a specifier who wants the access of a grid ceiling with the appearance of a fixed one.
E24/90. A variant of E24 with the rebate detailed for a ninety degree condition, used where panels meet at a corner or a change of plane and the standard rebate would not resolve cleanly.

Family three: the C profile

C is a profiled edge used where panels need to interlock or meet a perimeter detail rather than simply butt or drop in. It comes up on bespoke layouts and at junctions with walls, bulkheads and expressed structure. If your layout has a lot of non-standard perimeter, ask us to look at the drawing rather than guessing, because this is the profile most often specified wrongly.

Choosing without overthinking it

New build, flat substrate, want a seamless texture: B0.
Almost anything else on direct fix: B5. It is the safe answer and the one we recommend when there is no strong reason to go elsewhere.
Renovation, uneven existing structure, or a large hall wanting expressed module: B11.
Services above the ceiling that need regular access, grid can be visible: A24.
Services above the ceiling, grid must not be visible: E24, with E24/90 where geometry demands it.
Complex perimeter or interlocking layout: C, and send us the drawing.

What the profile does not change

Worth being clear about this. The edge profile does not alter the panel's fire classification. Standard Sonablock stays Euroclass B-s1,d0 to EN 13501-1 with CE marking under EN 13168 whichever edge you choose, and the same applies to the Sonablock FireSafe series, classified A2-s1,d0 in accordance with EN 13168:2012+A1:2015 for projects that mandate non-combustible.

Nor does the edge meaningfully alter absorption. Sonablock reaches αw 0.60 to 0.65, Absorption Class C, tested to EN ISO 354 by RISE Research Institutes of Sweden (report O100282), as a bare panel with a 200 mm air gap. What genuinely moves absorption is the cavity behind the panel, not the shape of its edge: as with all wood wool cement board, adding mineral wool into that cavity raises absorption substantially, and published data across the category shows Class A build-ups achieved that way. A suspension grid helps here, because it creates a deep void by definition.

Order it before you order the panels

Edge profile is a manufacturing choice, not something a carpenter adjusts on site. Cutting a rebate into a delivered square-edge panel does not work well and cutting a chamfer by hand never matches the factory edge. Decide the profile with the layout, not after the pallets arrive.

Panels come in 600 x 600, 1200 x 600 and 2400 x 600 mm at 15 or 25 mm thick, in Natural plus White RAL 9010, Light Grey RAL 7035, Dark Grey RAL 7004 and Black RAL 9011, with custom RAL and NCS on request.

Not sure which profile your ceiling wants? Send us the reflected ceiling plan and the substrate build-up and we will specify the edge, the fixing method and the pallet quantity. Full range and documentation in the Sonablock wood wool collection.